Cats will be trained to create self-imposed alterations in their hippocampal EEG in order to earn rewards. The altered hippocampal EEG will be brought under stimulus control by differential reinforcement techniques, and partial reinforcement methods will be used to make the conditioned EEG pattern highly resistant to extinction. The conditioned stimulus, which will control the occurrence of the altered EEG pattern, will subsequently be injected into behavioral test situations. This will allow some measurement of the behavioral concommitants of the altered EEG patterns. The methods used in this project are designed to control brain processes without resorting to techniques which depend on externally imposed, and sometimes irreversible, interference with the normal processes of the brain. Conditioned alterations of EEG are a way of controlling the normal regulatory circuits of the brain to provide the investigator with a way of selectively altering nervous system activity. It is hoped that these experiments will provide information about the significance of different frequency components of the hippocampal EEG. Both high and low frequency bands will be systematically manipulated in an attempt to study these rhythms from a unique vantage. Power spectral analysis will be used to analyze EEG patterns.